Highly efficient extraction of a proton beam by using bent single crystals

A substantially increased beam extraction efficiency can be achieved in the case of a multiple beam’s passage through a crystal. This suggestion was verified in experiments with short (5–7 mm long) curved single crystal with bending angles of 1.5–1.7 mrad performed at the Institute of High Energy Physics. The peak effiency values obtained were 47±3%, and the maximum average efficiency was 42±2% for a 23% intensity taken from an accelerated beam. The maximum extracted beam intensity was 6×10¹¹ protons per cycle.     

Effect of temperature on the fracture toughness of A516 Gr70 steel

Fracture toughness JIC and KIC tests were performed on A516 Gr70 carbon steel plate at the temperature ranging from −160°C to 600°C, and test results were analyzed according to ASTM E 813 and ASTM E 399. Unloading compliance J-integral tests were performed on ITCT specimens. The relation between the J_IC value and the test temperature was obtained. It was concluded that the temperature ranging from −15°C to 600°C is the upper shelf region of ductile-brittle transition temperature, and in this temperature range, fracture toughness J_IC values decreased with increasing temperature. The ductile brittle transition temperature of the material may be around −30°C. In the region near −30°C, the tendency of J_IC to decrease with decreasing temperature was significant.     

Resistance of a binderless cemented carbide to abrasion and particle erosion

A binderless cemented carbide has been evaluated in abrasion and erosion tests. The binderless carbide was compared with: SiC, Al₂O₃ and two conventional cemented carbides with 6% Co and different WC grain sizes (1 and 7 μm). In the abrasion tests, the materials were ground with silica, silicon carbide and diamond particles in the size range of 5–15 μm. The erosion tests were performed with 80, 200 and 600 μm silicon carbide erodents. The angle of impingement was 45° and the erodent velocity 70 m/s. In all tests, the conventional cemented carbides showed the highest, the binderless cemented carbide an intermediate and the ceramics the lowest wear resistance. Scanning electron and atomic force microscopy of the abraded surfaces revealed that the binderless cemented carbide was worn by a preferential removal of TiC grains. In erosion, the wear mechanism was largely plastic for the cemented carbides, whereas the ceramics were worn by micro-fracture. The SEM analysis also showed an impact scaling effect for the cemented carbides in erosion. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cooling performance of R510A in domestic water purifiers

In this study, the performance of R170/R1270 mixture was measured on a heat pump bench tester to substitute for R22. The tester was equipped with a hermetic compressor providing a nominal capacity of 3.5 kW. All tests were conducted under typical summer and winter conditions of 7/45°C and −7/41°C in the evaporator and condenser, respectively. During the tests, the composition of R170 varied from 0 to 10% with an interval of 2% for the R170/R1270 mixture. Test results showed that the capacities of the R1270 and R170/R1270 mixtures were 3.2–10.0% and 4.2–20.4% higher than those of R22, respectively. The coefficient of performance (COP) of R1270 was 2.7–3.6% higher than that of R22. On the other hand, the COP of R170/R1270 mixture decreased at a constant rate as R170 was added to R1270. The COP of R170/R1270 mixture was similar to that of R22 at 2% R170 and then became lower than those of R22 as R170 increased. For the mixture, the compressor discharge temperature was 8–20°C lower than that of R22. The amount of charge was reduced up to 55% compared with R22. Overall, pure propylene and R170/R1270 mixtures are good long-term candidates from the viewpoint of energy efficiency and greenhouse warming to replace R22 in residential air-conditioners and heat pumps.     

Wear Resistance of Ti–Fe Laminar Intermetallic Composites

Abstract—The wear resistance of Ti–Fe laminar intermetallic composites is compared with that of U9A and CrMoVSi1-1-1-1 tool steels. In the range 20–600°C, the wear resistance of the Ti–Fe composites is practically unchanged. Accordingly, it is below that of the tool steels at normal temperature, matches that of the steels at 500°C, and exceeds that of the U9A and CrMoVSi1-1-1-1 steels at 600°C (by factors of 2 and 1.6, respectively).     

Effect of Fluoride Content on Friction and Wear Performance of Ni<Subscript>3</Subscript>Al Matrix High-Temperature Self-Lubricating Composites

The self-lubricating composites Ni₃Al–BaF₂–CaF₂–Ag–Cr, which have varying fluoride contents, were fabricated by the powder metallurgy technique. The effect of fluoride content on the mechanical and tribological properties of the composites was investigated. The results showed that an optimal fluoride content and a balance between lubricity and mechanical strength were obtained. The Ni₃Al–6.2BaF₂–3.8CaF₂–12.5Ag–10Cr composite showed the best friction coefficients (0.29–0.38) and wear rates (4.2 × 10⁻⁵–2.19 × 10⁻⁴ mm³ N⁻¹ m⁻¹) at a wide temperature range (room temperature to 800°C). Fluorides exhibited a good reduced friction performance at 400 and 600°C. However, at 800°C, the formation of BaCrO₄ on the worn surface due to the tribo-chemical reaction at high temperatures provided an excellent lubricating property.     

Condensation heat transfer coefficients of HCFC22, R410A,R407C and HFC134a at various temperatures on a plain horizontal tube

In this study, external condensation heat transfer coefficients (HTCs) of HCFC22, R410A, R407C, and HFC134a were measured on a smooth horizontal tube at 30, 39, and 50°C with the wall subcooling of 3–8°C. The results showed that condensation HTCs decreased for all fluids tested with an increase in temperature. This is due mainly to such properties as the saturated liquid density and liquid thermal conductivity. These properties decrease as the temperature increase and accordingly HTCs decrease. The condensation HTCs of R410A are 9.2–19.7% higher than those of HCFC22 while those of R134a are 2.5–10.2% lower than those of HCFC22. Condensation HTCs of R407C, non-azeotropic mixture, are 29.4–34.3% lower than those of HCFC22. Overall, the HTCs of R407C are much lower than those of HCFC22, HFC134a and R410A due to the mass transfer resistance in a diffusion vapor film. Condensation HTCs of HCFC22 and HFC134a are higher than those calculated by Nusselt’s equation by 7.7–11.8% and 4.0–11.1% respectively. On the other hand, HTCs of R407C measured on plain tube, however, are not well predicted by these well-known prediction correlations due to the introduction of mass transfer resistance associated with non-azeotropic mixtures.     

High Temperature Tribological Characteristics of Fe–Mo-based Self-Lubricating Composites

Fe–Mo-based self-lubricating composites were prepared by a powder metallurgical hot-pressing method. The tribological properties of Fe–Mo-based composites with varied CaF₂ contents at high temperature were evaluated, and the effect of glaze films on the friction and wear characteristics of composites were analyzed. The results show that the introduction of CaF₂ into Fe–Mo alloys improved the mechanical properties, and the best tribological properties of Fe–Mo–CaF₂ composites were achieved at the CaF₂ content of 8 wt% at both room temperature and 600 °C. The worn surface of Fe–Mo–CaF₂ composite at 600 °C is characterized to plastic deformation and slight scuffing, and the improved tribological properties are attributed to the formation of lubricious glaze film that composed of high-temperature lubricants CaMoO₄ and CaF₂ on the worn surface of the composites.     

The Effectiveness of the ZDDP Tribofilms in Lubrication of Sol–Gel Titania in Technical Dry Friction Conditions

The objective of this study was the investigation of the tribological properties of the sol–gel derived titania modified by physically deposited zinc dialkyldithiophosphate (ZDDP) films. Titania coatings were prepared on silicon wafers Si(100) using sol–gel dip-coating method. Amorphous, anatase, and rutile titania were obtained in the post-preparation annealing process conducted at 100, 500, and 1000 °C, respectively. Deposition of ZDDP having butyl- (C4) or dodecyl- (C12) alkyl chain was performed by means of dip-coating (DC), self-assembly (SA), and Langmuir–Blodgett (LB) methods. The effectiveness of the modification was monitored by the wetting contact angle measurement. An increase of the surface hydrophobicity was observed upon modification. The surface topography, imaged with the use of Atomic Force Microscopy (AFM), revealed the presence of island-like agglomerates having different size of ZDDP films deposited using DC and SA method. Smooth and compact C12ZDDP films were observed when LB deposition was applied. The tribological performance of the ZDDP films on titania coatings was tested with the use of microtribometer operating in the normal loads range of 30–100 mN in the technical dry friction conditions. It was found that ZDDP tribofilms effectively decrease the coefficient of friction and effectively reduce the wear of titania coatings.     

Tribological Properties of Twin Electron-Beam Evaporated Cr–N and Al–Cr–N Coatings Under Laboratory Sliding and Drill Experiments

The tribological behavior of substoichiometric Cr–N and Al–Cr–N coatings prepared by twin electron-beam evaporation at 450 °C was studied. Al–Cr–N coatings with Al to Cr ratios in the range of 1–8 (and nitrogen concentrations of ~45 at.%) were synthesized and compared to Cr–N reference samples. The focus of this work is on Al–Cr–N (Al ≥ 30 at.%) coatings with the aim of (a) replacing Cr with Al due to environmental concerns and (b) achieving improved mechanical properties, and tribological performance. The composition, structure, mechanical and tribological properties of the coatings were determined using X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy in combination with nanoindentation measurements, laboratory controlled ball-on-disk sliding experiments, and wet and dry drilling experiments. It was found that all Al–Cr–N coatings exhibit higher hardness values compared to Cr–N coatings. Al–Cr–N coatings with Al contents and Al/Cr ratios of ≤38 at.% and ≤1.7, respectively, showed better performance than the rest of the coatings during both drilling and laboratory tribological experiments.     

Tribological properties of HVOF as-sprayed and heat treated Co–Mo–Cr–Si coatings

HVOF-sprayed Co–28%Mo–17%Cr–3%Si alloy tribological performance was tested in the as-sprayed condition and after thermal treatments at 200, 400, 600 °C for 1 h. As-sprayed coating possesses low hardness, undergoes adhesive wear against 100Cr6 steel and displays an high-friction coefficient causing relevant thermal effects. The 600 °C-heat treatment increases microhardness, thus preventing adhesive wear and reducing friction.     

Effect of Plasma Nitriding Environment and Time on Plain Fatigue and Fretting Fatigue Behavior of Ti–6Al–4V

Plasma nitriding was performed on Ti–6Al–4V fatigue test samples at 520°C in two environments (nitrogen and nitrogen–hydrogen mixture in a ratio of 3:1) for two time periods (4 and 18 h). Plain fatigue and fretting fatigue tests were conducted on unnitrided and plasma nitrided samples. Plasma nitriding degraded lives under both plain fatigue and fretting fatigue loadings. The samples nitrided in nitrogen exhibited superior lives compared with the samples nitrided in the nitrogen–hydrogen mixture, possibly due to the relatively higher hardness (and presumably lower toughness) of the nitrided layer of the samples nitrided in the nitrogen–hydrogen mixture environment. For those samples nitrided in the nitrogen–hydrogen mixture, those nitrided for 18 h exhibited superior lives compared with those nitrided for 4 h. This trend was observed for samples nitrided in nitrogen gas at lower stress levels only; the converse was true at higher stress levels of 550 MPa and 700 MPa under plain fatigue loading. However, under fretting fatigue loading, the plasma nitriding time did not influence the lives significantly.     

Tribological Properties of Reactive Magnetron Sputtered V2O5 and VN–V2O5 Coatings

Next generation of advanced hard coatings for tribological applications should combine the advantages of hard wear resistant coatings with low-friction films. In this study, the tribological behaviour of vanadium pentoxide (V₂O₅) single-layer as well as VN–V₂O₅ bi-layer coatings was investigated in the temperature ranging between 25 and 600 °C. For VN–V₂O₅ bi-layer coatings, the V₂O₅ top-layers were deposited by dc and bipolar-pulsed dc reactive magnetron sputtering, where the V₂O₅ phase shows preferred growth orientation in (200) and (110), respectively. The V₂O₅ single-layer coatings were prepared by dc reactive magnetron sputtering with a substrate bias of −80 V which leads to a preferred (200) growth orientation. Tribological properties were evaluated using a ball-on-disc configuration in ambient air with alumina balls as counterpart. The structure of the as-deposited films and eventual changes after tribometer testing were identified using X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The friction coefficient of VN–V₂O₅ bi-layer coatings deposited in dc and pulsed dc mode decreases from room temperature to 600 °C, where the pulsed dc VN–V₂O₅ coatings have a significantly lower coefficient of friction over the whole testing temperatures reaching a value of 0.28 at 600 °C. Up to 400 °C, V₂O₅ single-layer coatings showed almost the same coefficient of friction as pulsed dc VN–V₂O₅ bi-layer coatings but reached a value of 0.15 at 600 °C. It seems that thermal activation of crystallographic slip systems is necessary for V₂O₅ films to show a low-friction effect.     

Tribological Properties of Arc-Evaporated NbAlN Hard Coatings

Nb_1−x Al _x N hard coatings were synthesised by cathodic arc-evaporation with different Al contents to study its influence on the tribological properties. Ball-on-disc tests at temperatures up to 700 °C were performed and the recorded coefficient of friction was generally in the range from 0.8 to 1.0. Subsequent analysis of the coating wear track and the counterpart wear scar by optical profilometry and Raman spectroscopy revealed details on the wear behaviour of the tested coatings. The best wear performance for the Nb-rich coatings was in the temperature range of 300–500 °C, whereas at the maximum testing temperature the higher oxidation resistance with increasing Al content was beneficial in terms of wear resistance.     

A speckle-interferometric setup for determining the velocity of ultrasonic rayleigh waves on millimeter-size segments

The velocity of a Rayleigh wave was determined on 3–5 mm bases by measuring the changes in the distance between a transducer attached to an object and a laser-irradiated surface area. The propagation time of the wave from the transducer to this area was simultaneously measured. The distance and time were determined with resolutions of 0.1 μm and 1 ns, respectively. The setup was tested for plastically strained 45 steel specimens subjected to uniaxial tension. It was shown that the velocity measurement error is no larger than ±1% and that the correlation coefficient between the Rayleigh wave velocity and microscopic distortions in the crystal lattice is 0.89.     

Sliding Wear Characteristics of AZ91D Alloy at Ambient Temperatures of 25–200 °C

The dry sliding wear tests were performed for AZ91D alloy under the loads of 12.5–300 N and the ambient temperatures of 25–200 °C. We studied the wear characteristics of AZ91D alloy as a function of the normal load and the ambient temperature. The mild-to-severe wear transition occurred with increasing the load and the critical load reduced with the ambient temperature rising. However, no matter how high the ambient temperature was in the range of 25–200 °C, the mild wear prevailed under the lower loads. Especially, the AZ91D alloy presented a lower wear rate at 200 °C than at 25 and 100 °C under the low loads of 12.5–25 N, but vice versa under the loads of more than 25 N. These phenomena seem to be contradictory to the popular view that the mild-to-severe wear transition is controlled by the critical surface temperature. These may be attributed to a thick and hard mechanical mixing layer (MML) containing the mixture of MgAl₂O₄ and Mg on the worn surface. The MML thickened with increasing the ambient temperature (under the low loads), effectively reduced wear and markedly elevated the critical surface temperature. The oxidative wear and delamination wear successively predominated in the mild wear regime; the gross plastic-induced wear would prevail in the severe wear regime.     

Dialkyldithiophosphate Acids (HDDPs) as Effective Lubricants of Sol–Gel Titania Coatings in Technical Dry Friction Conditions

The goal of this study was the investigation of the effectiveness of dialkyldithiophosphate acids (HDDPs) films in improving the tribological properties of thin, sol–gel derived titania coatings. Amorphous, anatase, and rutile titania coatings were obtained using sol–gel dip–coating deposition after treatment at 100, 500, and 1,000 °C, respectively. Titania coatings were then modified from the liquid phase by HDDPs acids having dodecyl-(C₁₂), tetradecyl-(C₁₄), and hexadecyl-(C₁₆) alkyl chains deposited by dip–coating (DC) and Langmuir–Blodgett (LB) methods. The influence of the deposition procedure, the length of the HDDPs alkyl chain and the type of titania substrate on the surface morphology and tribological properties were studied. It was found, using wetting contact angle measurements, that these modifications of titania coatings decrease the surface free energy and increase its hydrophobicity. The surface topography imaged by Atomic force microscopy (AFM), exhibit island-like or agglomerate features for the DC deposition method, while smooth topographies were observed for LB depositions. Tribological tests were conducted by means of a microtribometer operating in the normal load range 30–100 mN. An enhancement of tribological properties was observed upon modification, as compared to unmodified titania.     

A pneumatic injector of deuterium pellets for fusion devices

A new deuterium pellet injector intended for maintaining a steady-state fusion reaction in a plasma is described. A technique for producing pellets by continuous solid deuterium extrusion was developed. A 2-mm-diameter cylindrical rod made from transparent solid deuterium was continuously pushed out of a screw extruder for 3000 s at a speed of 10–40 mm/s. Over 16000 deuterium pellets 2 mm in size were produced in the injector in the steady-state mode. They were continuously injected into the diagnostic chamber for 2000 s at a rate of 1–12 Hz and speed of 200–600 m/s. More than 12500 pellets were injected at a rate of 10 Hz in the steady-state mode, and 99% of them were intact.     

Removal of submicron aerosol particles and bioaerosols using carbon fiber ionizer assisted fibrous medium filter media

This paper reports the installation of a carbon fiber ionizer in front of a fibrous medium filter to enhance the removal of submicron aerosol particles and bioaerosols. Test particles (KCl) were classified with a size range of 50–600 nm using a differential mobility analyzer (DMA). The number concentration of the test particles was measured using a condensation particle counter (CPC). The average charge per particle was estimated by current measurements using an aerosol electrometer. At the face velocity of 0.5 m/s, the particle removal efficiency was 31.4% (for d_p=100 nm) when the ionizers were not operating but increased to 35.7% and 46.9% at 1.6×10¹¹ions/s and 6.4×10¹²ions/s with the ionizers, respectively. For the antibacterial tests, the test bioaerosols (E. coli) were aerosolized using a nebulizer and were deposited on the filter media for 5 minutes. After the deposited bioaerosols were exposed to unipolar air ions, they were incubated for 12 hours. The survival efficiency of E. coli was measured using a colony counting method. The survival fractions of E. coli exposed to positive air ions for 1, 5 and 10 minutes were 61.7%, 45.4% and 25.2%, respectively. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Jungho Hwang received his B.S. and M.S. degree in Department of Mechanical Engineering from Seoul National University, South Korea, in 1983 and 1985, respectively. He received his Ph.D. degree from UC Berkeley in 1991. Dr. Hwang is currently a Professor at the School of Mechanical Engineering at Yonsei University in Seoul, Korea. Dr. Hwang’s research interests include aerosols, air cleaning and thermal environmental engineering.     

Effect of Cu Content on the Structure,and Performance of Substoichiometric Cr–N Coatings

Cu–Cr–N coatings with Cu contents between 3 and 65 at.%, Cu/Cr ratios in the 0.04–4.5 range and 21–27 at.% N, synthesized by twin electron-beam Physical Vapor Deposition at 450 °C, were investigated and compared against substoichiometric Cr–N reference samples. The main objective of this study is to study the influence of Cu on the structure, and the subsequent effects on the mechanical properties, room (22 °C) and high temperature (500 and 840 °C) tribological performance of Cu–Cr–N coatings. Using X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and scanning electron microscopy, in combination with nanoindentation mechanical property measurements and laboratory-controlled ball-on-disc sliding experiments, it is shown that Cu–Cr–N coatings with low Cu content (3 at.%) possess sufficient wear resistance for high-temperature demanding tribological applications. The lubricious effect of oxide formation at high temperatures is also evaluated.